Ropivacaine Plasma Concentrations and Pharmacokinetics Following Erector Spinae Plane Block in the Pediatric Population

This pilot study will enroll patients at Texas Children's Hospital, aged 6 months to \<18 years scheduled to undergo a clinically indicated thoracic surgery with the adjunct of an erector spinae plane block for perioperative pain. A single shot erector spinae plane block is commonly offered for unilateral video-assisted thoracoscopic surgery (VATS) and unilateral chest tube insertions. Following parental consent and child assent to the block, participants will be assigned sequentially to either ropivacaine 0.2% at 0.3ml/kg or ropivacaine 0.5% at 0.3ml/kg. This pilot study poses no additional risk to the patient and the thoracic surgical procedures outlined are those for which an erector spinae plane block would be offered. Furthermore, the block dosing of 0.3ml/kg volumes with ropivacaine 0.2% or 0.5% are not outside of the standard of care or accepted dosages for peripheral nerve blocks. Venous sample serum ropivacaine levels will be collected prior to ESP block and at 30, 60, 90-minutes and 2, 4, 6 -hours from intravenous access in situ. A baseline alpha-1 acid glycoprotein (AGP) test will be collected and processed by TCH Pathology. Amide local anesthetics are predominantly protein bound to AGP. It is the unbound form that is active. While this study seeks to understand the pharmacokinetics of ropivacaine following a single shot erector spinae plane block, correlate of the AGP will simultaneously ascertain the free vs bound portion. Samples will be analyzed for the total and free serum ropivacaine concentrations. Pain scores will be collected from nursing records starting from arrival in the Post-Anesthesia Care Unit every 4 hours (up to 12 hours after arrival in PACU). Pain will be measured using The Face, Legs, Activity, Cry, Consolability scale (FLACC), the Wong-Baker FACES Pain Rating Scale (FACES), and the Visual Analogue Scale (VAS).